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The MIMO capacity of the geometrical Rayleigh fading channel in the presence of physical scattering is considered. This capacity assessment differs from most previous analyses where each element of the channel matrix, H, is preassigned as a circularly-symmetric complex-valued Gaussian random variable. By means of the directional mean and its associated standard deviation, we capture the spatial parameter in the model of interest into the nominal direction and angular spread. The impact of MIMO link capacity is then investigated by deriving an upper bound on the underlying mean capacity. Fortunately, the proposed upper bound provides deep insight into physical scattering because it can be shown as a deterministic function of the nominal direction and angular spread. Since it does not require any eigenvalue decomposition, the bound computation is thus very simple. Numerical examples are also conducted to illustrate not only the bound characterization with respect to sample mean capacity, but also the relationships of the bound to the indicated parameters.